Optically active physovenines were prepared from (-)- and (+)- eseroline respectively. Carbamates of the (-)-series were found to be potent inhibitors of ChE in vitro. Appropriate modification of the procedure allowed the preparation of novel sulfur analogs of physovenines, with a sulfur atom replacing the oxygen atom in ring C.Carbamates of the thia- series were found to be extremely potent inhibitors of ChE in vitro. Phenylcarbamates of (-)-eseroline, substituted in the phenyl group with alkyl groups, afforded compounds which were highly specific in their actions in inhibiting either AChE, or BChE.